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Friday, Oct. 12, 2012
Researchers hope to use Nobelist Yamanaka's breakthrough to restore people's eyesight
Riken to test iPS cells in human trial
By SIMEON BENNETT
Stem cells derived from a mouse's skin won Shinya Yamanaka the Nobel Prize in physiology or medicine on Monday. Now researchers in Japan are seeking to use his pioneering technology for an even greater prize: restoring sight.
Scientists at the Riken Center for Developmental Biology in Kobe plan to use induced pluripotent stem (iPS) cells in a human trial using patients with macular degeneration, a disease in which the retina becomes damaged and results in loss of vision, Yamanaka, a Kyoto University professor, told reporters the same day in San Francisco.
Companies including Pfizer Inc. are already planning trials of stem cells derived from human embryos, but Riken's will be the first to use a technology that mimics the power of embryonic cells while avoiding the ethical controversy that accompanies them.
"The work in that area looks very encouraging," John B. Gurdon, 79, a professor at the University of Cambridge who shared this year's Nobel Prize with Yamanaka, said in an interview in London.
Yamanaka and Gurdon split the 8 million Swedish kronor (about ¥94 million) award for experiments 50 years apart demonstrating that mature cells in latent form retain all of the DNA they had as immature stem cells, and that they can be returned to that potent state.
Their findings offer the potential for a new generation of therapies against hard-to-treat diseases like macular degeneration.
In a study published in 1962, Gurdon took a cell from a tadpole's gut, extracted the nucleus and inserted it into the egg cell of an adult frog whose own nucleus had been removed. The reprogrammed egg cell developed into a tadpole with the genetic characteristics of the original tadpole, and subsequent trials yielded adult frogs.
Yamanaka, 50, built on Gurdon's work by adding four genes to a skin cell from a mouse, returning it to its immature state as a stem cell with the potential to become any cell in the body.
He dubbed them induced pluripotent stem cells.
"There are few moments in science that are undisputed as genuine, elegant creativity and simplicity," said Alan Trounson, president of the California Institute for Regenerative Medicine in San Francisco.
"Yamanaka is responsible for one of those. An extraordinary accomplishment by a genuinely modest and brilliant scientist."
The technology may lead to new treatments against diseases such as Parkinson's by providing replacement cells.
"The implications for regenerative medicine are obvious," R. Sanders Williams, president of the Gladstone Institutes in San Francisco, where Yamanaka is a senior researcher, said. "Skin cells can be converted to any other cell you want — skin to brain or skin to heart."
While Gurdon and Yamanaka's achievements were groundbreaking, treatments based on iPS cells may still be "way down the line," Juleen Zierath, deputy chairwoman of the Nobel committee, told reporters in Stockholm on Monday.
Scientists first must ensure that the cells are safe, Yamanaka said in a video appearance from Japan at a news conference in San Francisco organized by Gladstone the same day. One concern is that stem cells could grow out of control, leading to cancers.
"We need to double-check we don't see any severe side effects in patients after transfer. That's where we have been spending most of our time," Yamanaka said.
"We are getting closer and closer. In some diseases, like macular degeneration, it's almost ready to go."
Researchers led by Masayo Takahashi at the Riken center plan to apply Yamanaka's technique to patients' skin cells in the human trial, turning them into stem cells before cultivating them to become a certain type of retinal cell. Those cells will then be transplanted into the patients' eyes, the Stem Cell News website reported in June, citing Takahashi.
Takahashi and his colleagues have already succeeded in transplanting retinal cells into mice, and none of the animals developed cancer, according to the report.
Yamanaka's work sidestepped the ethical controversy surrounding human embryonic stem-cell research, in which cells are extracted from an embryo that is destroyed in the process.
Pfizer, based in New York, plans to start a trial of an embryonic stem-cell therapy among patients with macular degeneration next year, according to the U.S. National Institutes of Health's clinicaltrials.gov website.
Geron Corp., a California-based company that started the first U.S.-approved trial of embryonic stem cells, said last November it was abandoning the program because of the costs.
Advanced Cell Technology Inc., located in Massachusetts, is also testing a treatment based on embryonic stem cells in patients with macular degeneration using a technique that doesn't destroy the embryo. Other companies such as Australia's Mesoblast Ltd. are testing adult stem cells derived from bone marrow in heart disease.
Apart from the ethical advantage, iPS cells are less likely to be rejected by a patient's immune system because the cells are their own, said Konrad Hochedlinger, a researcher at Harvard University's department of stem cell and regenerative biology.
"This method allows us to create patient-specific cells," Hochedlinger said.
Other applications may be to study diseases such as Alzheimer's or to test drugs against certain types of cells in a lab dish without the risks of side effects, according to Gurdon.
"If you can take cells from a patient, like a patient with a neurodegenerative disease, and grow those in culture in the laboratory, you can test drugs on them easily," Gurdon said.
"To be able to derive cells that reflect a disease, in culture, is immensely important."